Beef is by far the most costly protein when it comes to the environmental damage wreaked by feeding and raising cattle, according to a study out Monday.

Beef requires 28 times more land than the average total needed to produce either dairy, eggs, poultry or pork, said the research in the Proceedings of the National Academy of Sciences.

Raising beef also requires 11 times more irrigation water than other proteins, according to researchers at Bard College in New York, Yale University in Connecticut and the Weizmann Institute of Science in Rehovot, Israel.

Beef spews far more pollution into the environment, producing five times as many greenhouse gas emissions and six times the reactive nitrogen from fertilizer compared to the other proteins, the study found.

"Beef is consistently the least resource-efficient of the five animal categories," said the study, which said on average beef was about 10 times as costly as other proteins.

Beef also makes up about seven percent of all consumed calories in the US diet, it said.

To "most effectively" cut back on these environmental costs, the authors recommended "minimizing beef consumption."

Raising livestock for food is a practice that contributes to one fifth of global greenhouse gas emissions, and also pollutes water and interferes with biodiversity, according to the study authors.

Decade of US data

The study was based on a decade's worth of data on land, irrigation water, and fertilizer from the US Department of Agriculture, the Department of the Interior, and the Department of Energy.

Researchers used the 2000-2010 data to calculate the amount of resources needed to produce animal feed for each edible livestock.

About every 10 calories fed to poultry or pork accounted for one calorie consumed by humans. This ratio was nearly four times higher for beef.

Poultry, pork, eggs and dairy all added up to similar costs across the board, while beef was consistently the outlier.

They did not include fish in their study due to lack of data on feed use and the relatively small portion of calories (0.5 percent) it makes up in the average American diet.

Representatives of the US beef industry questioned the methodology of the study, and said environmental improvements have been made in recent years.

"The PNAS study represents a gross over-simplification of the complex systems that make up the beef value chain," said Kim Stackhouse, National Cattlemen's Beef Association director of sustainability research.

"The fact is the US beef industry produces beef with lower greenhouse gas emissions than any other country."

According to Amy Dickie, who led a study in April on agricultural strategies for cutting back on global warming, the findings are in line with recent research that has shown the high greenhouse gases involved in beef production.

"I am glad to see that the authors also considered water, nutrient, and land use which are all important resources and are intensively used by beef and dairy cattle," said Dickie, who works for the consulting firm California Environmental Associates.

"This information needs to get into the public domain so that people understand the consequences of their diet choices."